1. Field of the Invention
This invention relates to a fixing device in an image forming apparatus serving as, e.g., electrophotographic printer, photocopier, and facsimile machine and to such an image forming apparatus.
2. Description of Related Art
A belt type fixing device in an image forming apparatus such as, e.g., photocopier, printer, and facsimile machine forming monochrome or multicolor images has an endless fixing belt as described in, e.g., Japanese Patent Application Publication No. 2005-242111. The fixing belt is provided inside with a heating roller heating the fixing belt, a fixing roller rotationally driving the fixing belt, a pressure pad serving as a pressure member located on an upstream side of the fixing roller in a rotation direction of the fixing belt for pressing the fixing belt from an inner peripheral surface to an outer peripheral surface. A pressure roller is arranged outside the fixing belt. The pressure roller is disposed at a position facing to the fixing roller and the pressure pad via the fixing belt, thereby applying pressure to the fixing belt in a direction from the outer peripheral surface to the inner peripheral surface. The fixing belt is sandwiched with the fixing roller, the pressure pad, and the pressure roller to form a nipping portion serving as a contact range.
A medium on which toner images are transferred at the fixing device thus formed passes the nipping portion located between the fixing belt heated by means of the heating roller and the pressure roller and is fed, thereby fixing, to the medium, the toner images on the medium with applied heat and pressure.
With the fixing device in a prior art image forming apparatus, however, the pressure of the pressure pad serving as the pressure member becomes unstable during rotation of the fixing belt, thereby raising a problem that post-fixing images tend to be disordered.